The proposed experiments shall analyze by the ablation method the contribution of certain brain structures to visual processes in monkeys. More specifically, the role of the superior colliculus, pulvinar, and extrastriate visual cortical areas to attention, orientation, localization will be investigated by observing the visually guided behavior of monkeys in visual learning situations and recording eye movements before and after selective, surgical lesions of these structures. These experiments are relevant to recently-developed concepts of a mammalian tectothalamic pathway which may provide inputs into extrastriate cortical areas, and the findings may provide information concerning the role of the tectum and of this pathway in primate vision. Another related problem to be investigated is whether visual information needed for the performance of brightness, color and form discriminations may be conveyed to extrastriate visual areas independently of the geniculostriate system.